渗透对基坑水土压力的影响

基坑地基土中水的渗流不但可能引起渗透破坏，引起水压力，而且也对其土压力有重大影响，从而决定抗滑稳定性。本文作者针对有上层滞水、一般自由渗透、有承压水、基坑内排水与基坑外降水以及有超静孔压等情况对基坑支护结构物上的水土压力进行计算分析，结果表明：水土压力大小及分布与静水时的明显不同。且此时较宜于用库伦土压力理论。在有上层滞水情况下，用水土合算大体上是可以接受的。在有承压水情况下，其作为抗力的被动土压力可能丧失殆尽。基坑外人工降水与基坑内排水相比，更有利于基坑的稳定。正的超静孔压大大提高了土压力，负的超静孔压明显减少土压力。在很多有渗流的情况下，不宜用朗肯土压力计算土压力，而应当用库仑土压力理论的图解法来搜索可能滑裂面。

Influence of seepage on water and earth pressure in foundation pit

The seepage influence is calculated by using different methods under various conditions.It is found that the method for estimating water and earth pressure together is acceptable if suspended water exists.In the condition of the existence of confined water,the passive earth pressure will be reduced to about zero.The dewatering by means of well point outside of the pit can deduce active earth pressure and increases passive earth pressure which helps to slope stabilization of foundation pit.The positive excess hydrostatic water pressure elevates the earth pressure,while negative excess hydrostatic pressure will reduce the earth pressure.In most seepage condition,it is rather not to estimate the earth pressure with Rankine's theory but graphic method of Coulomb's theory by searching the possible slip surface.